This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 arising from an application entitled, A FLEXIBLE BINARY PHASE SHIFT KEYING/QUADRATURE PHASE SHIFT KEYING MODULATOR OF WIDEBAND CDMA SYSTEM, earlier filed in the Korean Industrial Property Office on Sep. 22, 1998, and there duly assigned Serial No. 1998-39294.
The present invention relates to a flexible modulator for binary phase shift keying/quadrature phase shift keying for a wide-band code division multiple access system. More specifically, the present invention relates to a flexible modulator for use in a binary phase shift keying (BPSK) method and a quadrature phase shift keying (QPSK) method for a wide-band code division multiple access system.
In a code division multiple access system, each signal of each subscriber has a common frequency transmitted by a frequency after multiplying by their own code, and spreading in a spectrum. In the case of a received signal, such a received signal is identified by reverse spreading and multiplying by their own codes, which is identical to the case of transmitting.
In the code division multiple access system, it is possible to increase the efficiency of frequency allocation by using a spreading spectrum and executing coding by multi-keying by their code.
Generally, the frequency spreading process decreases noise and an interference of the signal, but increases the required bandwidth. However, in the code division multiple access system, it is possible to accommodate a plurality of subscribers to one frequency by using a code, therefore an increase of the bandwidth due to spreading does not pose a significant drawback.
In the code division multiple access system, a channel which is used for transmission from a base station to a radio terminal is called a forward link, and a reverse channel is from the radio terminal to the base station is called a reverse link.
Typically, in the code division multiple access system, an interval between channels (channel spacing) is 5 Mhz. The bit error for transmission can be decreased by using a convolutional encoder, and an essential orthogonal code is allocated to each channel for identifying the forward link.
In the code division multiple access system, when direct sequence spreading is used, a chip rate is 4.096 Mega chip per second (Mcps), and each channel is modulated by a QPSK process after executing a BPSK process. But, the channel spacing is extended with a lager spreading rates.
A reverse channel comprises an access channel and a reverse traffic channel, and each channel has a reverse pilot channel. A mobile terminal transmits a reverse pilot channel synchronized with a pilot signal received from a base station. The reverse traffic channel also comprises a reverse information channel and a reverse signaling channel. These channels own jointly a CDMA frequency allocated by using a direct sequencexe2x80x94code division multiple access (DS-CDMA) technology. Each access channel and its reverse traffic channel is identified by an essential long code sequence of the subscriber.
FIGS. 1a and 1b illustrate a structure of a conventional access channel of a wideband CDMA system. A reverse link sequence 101(110) and a Hadamard code 102(111) have a same pseudo-noise chip rate (Rc). As shown in FIG. 1b, a modulation symbol rate input to reverse link sequence 110 is 64 ksps, 128 ksps, and 256 ksps for a system having a bandwidth of 3.5/5 MHz, 7/10/10.5 MHz, and 14/15 Mhz, respectively. A code rate (r) of a convolutional encoder 107 is 1/2, and a constraint length (k) is 7 or 9.
An access channel comprises a reverse pilot channel and a reverse access channel. The reverse pilot channel is used for determining the phase references of the reverse channel, an acquired channel, and a track channel in a base station.
FIGS. 1a and 1b show the reverse pilot signal s(t) 105 (114) comprises a non-modulated long code sequence. FIG. 1a shows a pilot channel composed of zeros is converted by a reverse link sequence 101, and then divided into an in-phase signal (I) and a quadrature signal (Q). Each divided signal (I and Q) is spread out by using a Hadamard code H0 and H1 102, respectively, and passed by a baseband filter 103, and multiplied by cos(2pfct) and sin(2pfct) 104, respectively. Finally, after summing together the two multiplied I and Q signals 105 together, the composite signal s(t) 105 is output for transmitting.
FIG. 1b illustrates the structure of a reverse access channel. An information bit of the reverse access channel is 154 bits per frame (or 152 bits per frame) while the constraint length k is 9.
The information bit of the access channel generated with 7.7 (or 7.6) kbps is added by 6 (or 8) bits for encoding at adder 106, and is then output to a convolutional encoder 107 at a speed of 8 kbps.
The convolutional encoder 107 constantly maintains a symbol rate of 16 kilo symbols per second (ksps) by iterating input bits as the occasion demands for error correction.
A block interleaver 108 writes a code symbol received from the convolutional encoder with a unit of columns, and reads with a unit of rows.
A symbol repeater 109 iterates each block interleaved symbol as required for an access channel having a fixed data rate, and the iterated signal is constantly maintained with a speed of a modulation symbol rate.
The iterated signal is converted by a reverse link sequence 110, and then is divided into an in-phase signal (I) and a quadrature signal (Q).
Each divided signal (I and Q) is spread out by using a Hadamard code H0 and H1 respectively 111, passed by a baseband filter 112, multiplied by one of cos(2pfct) and sin(2pfct) 113, respectively. Finally the two multiplied I and Q signals are summed together and output as a composite signal s(t) 114 for transmission.
FIGS. 2a and 2b illustrate a reverse traffic channel structure with a single signal mode in a conventional wideband code division multiple access system. The reverse traffic channel operates at four kinds of variable data rates, and a reverse information channel operates at 16, 32 and 64 kbps. A signaling channel operates at 2 and 4 kbps.
FIG. 2a illustrates the structure of a reverse pilot power control signaling (PPCS) channel. The pilot information (all zeros), power control information, redundant information bit, and a signaling channel information are all modulated.
The pilot channel bit, which is composed of zeros, is directly transferred to multiplexer 201. The power control information bit, which has 10 bits per frame, is transferred to the multiplexer 201 via a quadruple symbol repeater 202.
The signaling channel information bit having 74 bits (or 72) bits per frame is added with a predetermined number of bits (e.g. 6 or 8 bits) for encoding, then is encoded convolutionally by encoder 204; the information output from encoder 204 is block interleaved 205, iterated by a symbol repeater 206, and subsequently transferred to multiplexer 201.
The multiplexer 201 generates a spread symbol with 16 ksps after a time division multiplexing bits of a pilot channel with 4 ksps, a power control information channel with 2 ksps, and a redundant information channel with 2 ksps, and a signaling channel information channel with 8 ksps.
The generated spread symbol is transferred to a symbol post-repeater 207. The iterated signal by the symbol post-repeater 207 is converted by a reverse link sequence 208 and then divided into an in-phase signal (I) and a quadrature signal (Q).
Each divided signal (I and Q) is spread out by using a Hadamard code H0 and H1 respectively 209, passed by a baseband filter 210, and multiplied by one of cos(2pfct) and sin(2pfct) 211, respectively. Finally, the multiplied I and Q signals are summed together and the composite signal is output as signal s(t) for transmission.
FIG. 2b illustrates the structure of a reverse information traffic channel. A reverse traffic channel information bit is output from convolutional encoder 213 to symbol puncturing means 214 for clearing certain symbols necessary for an agreement of the data rates.
A signal, which is input to the symbol puncturing means 214, is then output to a serial to parallel converter 216 via a symbol pre-repeater 215. The serial to parallel converter 216 receives a BPSK data from the symbol pre-repeater 215 and supplies two parallel binary data stream I and Q signals.
The parallel converted I and Q signals are iterated in a symbol post-repeater 217 and converted to QPSK data.
The QPSK converted I and Q signals are converted by a reverse link sequence 218, and then spread out by using a Hadamard code H2 and H3 219, respectively, and passed by a baseband filter 220, and multiplied by one of cos(2pfct) and sin(2pfct) 211, respectively. Finally, after summing the two multiplied I and Q signals together, the composite signal is output as signal s(t) 222 for transmission.
FIG. 3a through FIG. 3c illustrates a reverse traffic channel structure with a multiple signal mode in a conventional wideband code division multiple access system. In FIG. 3a, symbol repeater 302, adder 303, convolutional encoder 304, block interleaver 305, symbol repeater 306, symbol post repeater 307, reverse link sequence 308, Hadamard spreading unit 309, baseband filter 310, multiplier 311, and output signal 312 all operate as discussed in FIG. 2a. A reverse traffic channel is added to the reverse traffic channel structure with a multiple signal mode.
As illustrated in the FIGS. 3b and 3c, a nth (and mth) reverse traffic channel executes convolutional encoding at 313 (323) of n (and m) information bits of the reverse traffic channel, symbol puncturing 314 (324), and symbol pre-iteration 315 (325), serial to parallel conversion 316 (326), and symbol post-iteration 317 (327).
The symbol post-iterated I and Q signals are converted by a reverse link sequence 318. The I signal is spread out by using a Hadamard code H2n and the Q signal is spread out by using a Hadamard code H2n+1 or H2n+1 319 (329).
The I and Q signals are output to baseband filter 320 (330), and multiplied by one of cos(2pfct) and sin(2pfct) 321 (331), respectively. Finally, after summing the two multiplied I and Q singals together, a composite signal s(t) 322 (332) is output for transmission.
FIG. 4a and FIG. 4b illustrates a structure of a packet access channel in a wideband code division multiple access system. The operation of the pilot channel of the FIG. 4a is same to the FIG. 1a, whereby a pilot signal comprised of all zeros is converted by reverse link sequence 401, and subsequently divided into an in-phase signal (I) and a quadrature signal (Q). Hadamard encoding unit 402, baseband filter 403, multiplier 404, and the summing of the multiplied signals as composite signal s(t) 405 all operate as previously indicated in the discussion of FIG. 1a. 
As illustrated in the FIG. 4b, an information bit of the packet access channel with 34 (or 32) bits per frame is added with 6 (or 8)a bits for encoding at adder 406, and is subsequently convolutionally encoded 407, block interleaved 408, and iterated at symbol repeater 409. Finally, a spreading sequence is performed by a reverse link sequence 410 and a Hadamard coding unit 411, baseband filter 412, multiplier 413, and output for transmission as composite signal 414.
FIG. 5a and FIG. 5b illustrate a structure of a reverse packet traffic channel in a wideband code division multiple access system. A packet signaling channel information bit is added with 6 (or 8) bits for encoding at adder 502, convolutionally encoded at encoder 503, block interleaved at unit 504, iterated by symbol repeater 505, and output to multiplexer 501.
The multiplexer generates 501 a spread symbol by executing a time divisional multiplexing a non-modulated signal of the pilot channel and a symbol iterated signal of the packet signaling channel.
The spread symbol is iterated again by symbol post-repeater 506 and is spread by a reverse link sequence 507 and a Hadamard code 508. The baseband filter 509, multiplier 510, and composite output signal s(t) 511 are the same as previously described in the discussion of FIG. 4b. 
As illustrated in FIG. 5b, an information bit of the reverse packet traffic channel is input for convolutional encoding 512, and then is subsequently block interleaved 513. The block interleaved signal is subsequently input to symbol repeater, converted to parallel from serial 515, and converted to QPSK. Finally, a spreading by reverse link sequence 517 and a Hadamard coding unit to the I and Q signals 518. The baseband filter 519, multiplier 520, and the output composite signal s(t) are the same as previously described in the discussion of FIG. 4b. 
A forward wideband code division multiple access channel comprises a pilot channel, a synchronous channel, and paging channels more than 8, and numbers of forward traffic channels.
The forward traffic channel comprises a forward information channel and a forward signaling channel.
Each code channel is executed using orthogonal spreading by an appropriate Walsh code and is executed second spreading with a chip rate of 4.096 Mcps by a pseudo-noise sequence.
The forward pilot channel, the signaling channel and a power control channel and a spare information channel are identified each other by a forward power control signaling (PCS) channel.
Hereinafter, an embodiment of the conventional forward wideband CDMA channel is illustrated. A forward link sequence and a Hadamard code have a same pseudo-noise chip rate (Rc) and a modulation symbol rate is 64 ksps, 128 ksps for a system having a bandwidth of 3.5/5 MHz, 7/10/10.5 MHz, respectively. A code rate (r) of a convolutional encoder is 1/2, and a constraint length (k) is 7 or 9.
FIG. 6a through FIG. 6e illustrate a structure of a forward channel in a conventional wideband code division multiple access system.
FIG. 6a illustrates a channel structure of a forward pilot channel and a synchronous channel. The pilot channel that is a non-modulated spread spectrum signal is transmitted by an activated base station and used for tuning a radio terminal activated in a coverage area of a base station.
As shown in FIG. 6a, the pilot channel composed of zeros is spread out by using a Hadamard coding unit H0 601 and then divided into an in-phase signal (I) and a quadrature signal (Q).
The divided signal I is spread out by a forward link I channel sequence 602 and multiplied at multiplier 604 by cos(2pfct) via a baseband filter 603.
The divided signal Q is spread out by a forward link Q channel sequence 602 and multiplied at multiplier 604 by sin(2pfct) via the baseband filter 603. Finally, after adding the two multiplied I and Q signals, a composite signal s(t) 605 is output for transmission.
A bit rate for the forward synchronous channel is 16 kbps. And, for a same base station, a pilot pseudo-noise sequence of I and Q channel for the forward synchronous channel is same to the pilot pseudo-noise sequence offset of a pilot channel.
Accordingly, the synchronicity of a synchronous channel can be found by searching a pilot channel and taking a pilot pseudo-noise sequence.
As shown in FIG. 6a, the forward synchronous channel bit is added by 6 or 8 bits by adder 606 for encoding, convolutionally encoded at encoder 607, block interleaved at block interleaver 608, converted from serial to parallel at converter 609, subsequently converted to QPSK by executing a symbol post repeater 610, and is spread out by a Hadamard coding unit H1 611.
The spread I and Q signals are spread out by a forward link I channel sequence and a forward link Q channel sequence 612, respectively, are multiplied by multiplier 614 by cos(2pfct) and sin(2pfct), respectively, after being output from the baseband filter 613. Finally, after summing together the two multiplied I and Q signals, a composite signal s(t) 615 is output for transmission.
A forward paging channel transmits an information at 16 kbps data rates.
A frame of the paging channel is held for 5 ms. The paging channel has a paging channel slot with a size of 20 ms.
In one base station, the paging channel and the pilot channel use a same pilot pseudo-noise sequence.
As shown in FIG. 6b, the forward paging channel bit is added with 6 or 8 bits by adder 616b for encoding, is convolutional encoded at encoder 617, block interleaved at block interleaver 618, and converted from serial to parallel at converter 619, converted to QPSK by executing a symbol post repeater (620), and is spread out by a Hadamard code Hm at Hadamard coding unit 621, where m is a value between 2 through 5 (621).
The spread I and Q signals are spread out by a forward link I channel sequence and a forward link Q channel sequence 622, respectively, multiplied at multiplier 621 by one of by cos(2pfct) and sin(2pfct), respectively, after being output from baseband filter 623. Finally, after summing together the two multiplied I and Q signals, a composite signal s(t) 625 is output for transmission.
During call service, the forward traffic channel is used for transmitting and signaling information to a specific radio terminal.
For the forward traffic channel, a base station transmits information with variable data rates of 64, 32 and 16 kbps, holds a constant speed of 64 kbps by a symbol puncturing means.
A channel frame of the forward traffic channel has an interval of 5 ms and a pilot pseudo-noise sequence and a pilot pseudo-noise sequence offset, which is the same for the pilot channel of a same base station.
The forward traffic channel uses data scrambling and a pseudo-noise sequence having a long period. The pseudo-noise sequence is allocated to each subscriber and has a period of 242 B1 chips.
As shown in FIG. 6c, the forward traffic channel bit is convolutionally encoded at encoder 626, and is held by symbol puncturing means 627. A scramble code generator 628 generates scrambling codes by using the scrambling code seed supplied for a traffic channel n.
The punctured symbol is added to the scrambling code at 629. The scrambling code having the punctured symbol is converted from serial to parallel at converter 630, converted to QPSK by symbol repeater 631, and is spread out by a Hadarnard coding unit Hn 632.
The spread I and Q signals are spread out by a forward link I channel sequence and a forward link Q channel sequence respectively 633, are multiplied by multiplier 632 by one of cos(2pfct) and sin(2pfct), respectively, being output from baseband filter 634. Finally, after summing the two multiplied I and Q signals, a composite signal s(t) 636 is output for transmission.
FIG. 6d illustrates a channel structure of the forward signaling information channel and power controlling/spare information channel.
As shown FIG. 6d, an information bit of the forward signaling channel is added with 6 or 8 bits for encoding by adder 637, is convolutionally encoded at encoding unit 638, is block interleaved at block interleaver 639, and is repeated by symbol repeater 640.
The power controlling/spare information symbol executes a symbol iteration at symbol repeater (4xc3x97) 646 for making the symbol rates identical to the forward signaling channel. An additional a symbol iteration from symbol repeater (4xc3x97) 646 to symbol repeater 640 is performed for making the symbol rates identical to modulation symbol rates output by symbol repeater 647.
The iterated signaling information bit and the power controlling/spare information symbol is spread out by a Hadamard code Hk (641).
The spread iterated signaling information bit and the power controlling/spare information symbol are spread out by a forward link I channel sequence and a forward link Q channel sequence respectively 642, multiplied at multiplier 644 by one of cos(2pfct) and sin(2pfct), respectively, after being output from baseband filter 643. Finally, after summing the two multiplied I and Q signals together, a composite signal s(t) 645 is output for transmission.
The signaling information bit and the power controlling/spare information symbol spread out by the Hadamard code can be exchanged with each other is required in accordance with call service by subscribers.
FIG. 6e illustrates a channel structure of the forward packet traffic channel. The forward packet traffic channel bit is convolutionally encoded at encoder 646, is block interleaved at block interleaver 647, added with a scrambling code 648 generated by the scrambling code generator at adder 649.
The scrambled signal is converted from serial to parallel at converter 650, and is converted to QPSK by symbol repeater 651, and is spread out by a Hadamard coding unit Hp 652.
The spread I and Q signals are spread out by a forward link I channel sequence and a forward link Q channel sequence 653, respectively, multiplied at multiplier 655 by one of cos(2pfct) and sin(2pfct), respectively, after being output from baseband filter 654. Finally, after summing the two multiplied I and Q signals, a composite signal s(t) 656 is output for transmission.
As illustrated in the above figures, the internal blocks of each channel in the conventional wideband code division multiple access channel have blocks performing similar functions between the channels.
However, there are some parts for holding commonality between a forward channel and a reverse channel.
But, since the above channels are constructed by an independent hardware, especially ASIC (Application Specific Integrated Circuit), a large number of gates are needed to perform redundant functions.
This large number of gates has causes a problem of decreasing the ASIC reliability and increasing the power consumption.
It is an object of the present invention for solving the above problems of decreased reliability and increased power consumption by providing a flexible modulator as a means for controlling a similar parts of a wideband code division multiple access (W-CDMA) channel by an external register which permits the flexible modulator for executing a binary phase shift keying (BPSK) and a quadrature phase shift keying (QPSK) capable of controlling common channels.
According to the present invention, a preferred embodiment of a flexible modulator for binary phase shift keying and quadrature phase shift keying in a wideband code division multiple access system comprises:
a first link selecting means for selecting a modulating type after receiving a signal of a reverse channel or an I (In-phase) signal and Q (quadrature) signal of a forward channel for which a spread modulation is to execute;
Hadamard spreading means for a Hadamard code spreading modulation after receiving said I and Q signals from the first link selecting means;
exchanging means for exchanging signal paths of the Hadamard spread I and Q signals when an exchange for the forward signal is needed; and,
spreading means for executing a spread modulation for a pseudo-noise (PN) code of the exchanged I and Q signals.
In the above embodiment, it is preferable that the first link selecting means receives a signal to be spread out of a reverse pilot power control signaling (PPCS) channel.
It is also preferable that the first link selecting means receives said I and Q signals to be spread out of a forward power control signaling (PCS) channel.
It is also preferable that the first link selecting means comprises:
an I multiplexer for selecting a reverse I signal when a channel operating mode is a reverse channel mode and for selecting a forward I signal when the channel operating mode is a forward channel mode;
a Q multiplexer for selecting a reverse I signal when a channel operating mode is a reverse channel mode and for selecting a forward Q signal when the channel operating mode is a forward channel mode, and
a symbol repeater for executing a symbol iteration for said I signal received from the I multiplexer and said Q signal received from the Q multiplexer.
It is preferable that an iteration rule of the symbol repeater is determined by a channel bandwidth and a type of channels.
It is preferable that the Hadamard spreading means comprises:
an I Hadamard spreader for spreading the reverse or the forward I signal by a first Hadamard code, and
a Q Hadamard spreader for spreading the reverse Q signal by a second Hadamard code and the forward Q signal by the first Hadamard code.
It is preferable that the psuedo-noise (PN) code spreading means comprises:
an I psuedo-noise (PN) code spreader for spreading the reverse or forward I signals by a first PN code, and
a Q PN spreader for spreading the reverse Q signal by the first PN code and the forward Q signal by a second PN code.
According to the present invention, a second preferred embodiment of a flexible modulator for binary phase shift keying and quadrature phase shift keying in a wideband code division multiple access system comprises:
a first link selecting means for selecting a modulating type after receiving a signal of a reverse channel or an I (In-phase) signal and Q (quadrature) signal of a forward channel for which a spread modulation is to execute;
Hadamard spreading means for a Hadamard code spreading modulation after receiving said I and Q signals from the first link selecting means; and,
spread modulation means for executing a spread modulation for a pseudo-noise (PN) code of the Hadamard spread I and Q signals.
In the second embodiment, it is preferable that the first link selecting means is connected to a forward traffic channel signal to be spread out.
In a variation of the second embodiment, it is also preferable that the first link selecting means is connected to a forward synchronous channel signal to be spread out.
It is also preferable that the first link selecting means is connected to a forward paging channel signal to be spread out.
It is also preferable that the first link selecting means is connected to a reverse traffic channel signal to be spread out.
It is preferable that the first link selecting means is connected to a reverse access channel signal to be spread out.
In the second embodiment, It is preferable that the first link selecting means comprises:
a serial to parallel converter for converting the reverse or forward channel signal to be spread out to 2 bits parallel and transferring to the I multiplexer and Q multiplexer respectively;
an I multiplexer for selecting the reverse or forward channel signal to be spread out, if a transfer rates are under the 32 kbps and 80 kbps in 5 Mhz and 10 Mhz bandwidth respectively in a reverse operation mode and selecting an output signal of the serial to parallel converter if not;
a Q multiplexer for selecting the reverse or forward channel signal to be spread out, if a transfer rates are under the 32 kbps and 80 kbps in 5 Mhz and 10 Mhz bandwidth respectively in a reverse operation mode and selecting an output signal of the serial to parallel converter if not; and,
a symbol repeater for executing a symbol iteration for the transferred signals from the I multiplexer and Q multiplexer.
It is preferable that the Hadamard spreading means comprises:
an I Hadamard spreader for spreading the reverse or the forward I signal by first Hadamard code, and
a Q Hadarnard spreader for spreading the reverse Q signal by the second Hadamard code and the forward Q signal by the first Hadamard code.
It is preferable that the PN code spreading means comprises:
an I PN code spreader for spreading the reverse or forward I signals by the first PN code, and
a Q PN spreader for spreading the reverse Q signal by the first PN code and the forward Q signal by the second PN code.